1. Field of the Invention
The present invention relates to a spindle motor and a data recording/reproducing apparatus that has the spindle motor.
2. Description of the Related Art
Data recording/reproducing apparatuses, such as hard disc drives, find an expanding use. They are used in storage apparatus of large capacity and desktop personal computers. Further, they are incorporated in electronic apparatuses such as notebook personal computers and portable terminal devices.
Recently, hard disc drives of PC card type have come into use. A hard disc drive of this type has a so-called PC (Personal Computer) card size, or the same size as an IC (Integrated Circuit) memory card and a card-type modem. A user may insert the hard disc drive of PC card type into the PC card slot of his or her personal computer or portable terminal device and may use this hard disc drive, whenever necessary.
FIGS. 1 and 2 show two motors for use in conventional hard disc drives.
The motor shown in FIG. 1 comprises a rotor 1000 and a stator 1001. The rotor 1000 holds a disc-shaped recording medium D. The rotor 1000 is rotatably mounted on the shaft 1002 of the stator 1001 by means of two ball bearings 1003 and 1004.
In the motor shown in FIG. 2, the rotor 1010 holds a disc-shaped recording medium D and is rotatably mounted on the shaft 1012 of the stator 1011 by means of two ball bearings 1013 and 1014.
The motors of such structures as described above are disadvantageous in the following respects.
The motor of FIG. 1 cannot a small thickness E1 along the shaft, because the ball bearings 1003 and 1004 are arranged along the shaft 1002 (in the thrust direction). Similarly, the motor of FIG. 2 has a relatively large thickness E2 along the shaft, because the ball bearings 1013 and 1014 are arranged along the shaft 1012.
In both motors illustrated in FIGS. 1 and 2, the drive magnet 1020 surrounds the drive coil 1030. Besides, the coil 1030 is wound around a core.
It is therefore difficult to reduce the thickness E1 of the motor shown in FIG. 1 and the thickness E2 of the motor shown in FIG. 2. To make matters worse, either motor may not be sufficiently resistant to external impacts, because the two ball bearings are arranged in the thrust direction. When an impact is applied to the motor, data may not be reliably recorded or reproduced on and from the disc-shaped recording medium D.
In view of the forgoing, an object of this invention is to provide a spindle motor that is thin, has a simple structure, excels in impact resistance and exhibits high operating reliability, and to provide a data recording/reproducing apparatus that has such a spindle motor.
A spindle motor having a rotor and a stator for rotating the rotor. The rotor comprises: a shaft; a rotor housing formed integral with the shaft and configured to hold an object to be rotated; a rotor yoke formed integral with the rotor housing and made of magnetically permeable material; and a drive magnet secured to the rotor yoke. The stator comprises: a stator housing; a first bearing held in the stator housing and supporting the first the shaft, allowing the shaft to rotate; a second bearing provided between the stator housing and the rotor housing, arranged concentric to the first bearing in a radial direction, and supporting the rotor, allowing the rotor to rotate; a stator yoke formed integral with the stator housing, constituting a part of a housing containing the rotor and the stator, and made of magnetically permeable material; and a drive coil mounted on the stator yoke and arranged in face-to-face relation with the drive magnet.
In the spindle motor, the rotor housing is formed integral with the shaft and configured to hold an object to be rotated. The rotor yoke is formed integral with the rotor housing and made of magnetically permeable material. The drive magnet is secured to the rotor yoke. The first bearing of the stator is held in the stator housing and supports the first the shaft, allowing the shaft to rotate. The second bearing is provided between the stator housing and the rotor housing, arranged concentric to the first bearing in a radial direction, and supports the rotor, allowing the rotor to rotate. The stator yoke is formed integral with the stator housing and constitutes a part of a housing that contains the rotor and the stator. The stator yoke is made of magnetically permeable material. The drive coil is mounted on the stator yoke and arranged in face-to-face relation with the drive magnet.
The second bearing is provided between the stator housing and the rotor housing, arranged concentric to the first bearing in a radial direction. That is, the first bearing and the second bearing are arranged in the radial direction. The spindle motor can therefore be thinner in the axial direction than in the case where two bearings are arranged in the thrust direction as in the conventional spindle motor.
The spindle motor can be still thinner, because the stator yoke is made of magnetically permeable material and constitutes a part of a housing that contains the rotor and the stator. Moreover, the drive coil is arranged in face-to-face relation with the drive magnet. This also helps to render the spindle motor thinner in the axial direction, than in the conventional spindle motor in which the drive coil faces the circumferential surface of the drive magnet.
Thus, the spindle motor can be very thin in the axial direction and very simple in structure.
As another feature of the spindle motor, the first bearing can be a sintered metal bearing, and the second bearing can be a ball bearing. Since the first bearing can be a sintered metal bearing, the spindle motor is excels in resistance to external impacts. In other words, only one ball bearing would be used, the motor would be more resistant to impacts than the conventional spindle motor that has two ball bearings.
As another feature of the spindle motor, the stator yoke can be a silicon steel plate or an iron plate, and the drive coil can be formed integral with an inner surface of the stator yoke. When the drive coil is formed integral with the inner surface of the stator yoke, the spindle motor can be thinner than otherwise.
In the spindle motor according to claim 4, which is a modification of the motor defined in claim 2, the sintered metal bearing is a dynamic-pressure fluid bearing.
A data recording/reproducing apparatus comprises a spindle motor having a rotor and a stator for rotating the rotor. The rotor comprises: a shaft; a rotor housing formed integral with the shaft and configured to hold a disc-shaped recording medium to be rotated; a rotor yoke formed integral with the rotor housing and made of magnetically permeable material; and a drive magnet secured to the rotor yoke. The stator comprises: a stator housing; a first bearing held in the stator housing and supporting the first the shaft, allowing the shaft to rotate; a second bearing provided between the stator housing and the rotor housing, arranged concentric to the first bearing in a radial direction, and supporting the rotor, allowing the rotor to rotate; a stator yoke formed integral with the stator housing, constituting a part of a housing containing the rotor and the stator, and made of magnetically permeable material; and a drive coil mounted on the stator yoke and arranged in face-to-face relation with the drive magnet.
In the apparatus, the rotor housing is formed integral with the shaft and configured to hold an object to be rotated. The rotor yoke is formed integral with the rotor housing and made of magnetically permeable material. The drive magnet is secured to the rotor yoke. The first bearing of the stator is held in the stator housing and supports the first the shaft, allowing the shaft to rotate. The second bearing is provided between the stator housing and the rotor housing, arranged concentric to the first bearing in a radial direction, and supports the rotor, allowing the rotor to rotate. The stator yoke is formed integral with the stator housing and constitutes a part of a housing that contains the rotor and the stator. The stator yoke is made of magnetically permeable material. The drive coil is mounted on the stator yoke and arranged in face-to-face relation with the drive magnet.
The second bearing is provided between the stator housing and the rotor housing, arranged concentric to the first bearing in a radial direction. That is, the first bearing and the second bearing are arranged in the radial direction. The spindle motor can therefore be thinner in the axial direction than in the case where two bearings are arranged in the thrust direction as in the conventional spindle motor.
The spindle motor can be still thinner, because the stator yoke is made of magnetically permeable material and constitutes a part of a housing that contains the rotor and the stator. Moreover, the drive coil is arranged in face-to-face relation with the drive magnet. This also helps to render the spindle motor thinner in the axial direction, than in the conventional spindle motor in which the drive coil faces the circumferential surface of the drive magnet.
The spindle motor can be very thin in the axial direction and very simple in structure.
As another feature of the data recording/reproducing apparatus, the first bearing can be a sintered metal bearing, and the second bearing is a ball bearing. Since the first bearing can be a sintered metal bearing, the spindle motor would excel in resistance to external impacts. In other words, only one ball bearing would be used, the motor would become more resistant to impacts than the conventional spindle motor that has two ball bearings.
As another feature of the data recording/reproducing apparatus, the stator yoke can be a silicon steel plate or an iron plate, and the drive coil can be formed integral with an inner surface of the stator yoke. Since the drive coil would be formed integral with the inner surface of the stator yoke, the spindle motor can be thinner than otherwise.
As another feature of the data recording/reproducing apparatus, the sintered metal bearing can be a dynamic-pressure fluid bearing. Since the sintered metal bearing can be a dynamic-pressure fluid bearing, it would reduce the probability that the shaft vibrates. The spindle motor can therefore be used to rotate the disc-shaped recording medium at high speeds, making but a little noise.
As described above, the present invention can provide a spindle motor that is thin, has a simple structure, excels in impact resistance and exhibits high operating reliability, and also a data recording/reproducing apparatus that has such a spindle motor.